1. Field of the Invention
The present invention is related to a pressure detecting apparatus made by three-dimensional (3D) printing technologies. More particularly, the present invention is related to a pressure detecting apparatus made by 3D printing technologies which is able to be used in dangerous areas.
2. Description of the Prior Art
Fiber is advantaged in thin, light, anti-electromagnetic influence, signal transmission/transduce, and high temperature/cauterization resistance. Its diameter is only from several decades to hundreds micro meters. Fiber has many advantages such as free from electromagnetic influence, low optical power loss, easy to be placed, one line corresponding to multi-points for multi-measurements. Thus fiber measurement technologies are widely accepted. Recently, fiber optic interferometric sensor system is applied to measure tiny variation of many things.
Fiber grating transducer is advantaged in that only the reflection signal of the fiber grating is important when it is connected to control system. The fiber grating has excellent resolution and range, and is water-resist and cauterization-resist. Also, fiber grating can apply measurement by wavelength coding signal.
If a fiber grating is made in a fiber, a fiber grating can be retrieved. Interference would make light propagation in fiber (modulus propagation constant) be influenced and generate another propagation method.
Recently, sensor is directly written into fiber to make a fiber Bragg grating, FBG. Fiber Bragg grating applies Bragg reflection principle. When light passes through area with periodically changed index of refraction, portion of reflection would be generated on each interface. If the period just meets condition of “all added portion of reflections presents as in phase”, or a round trip of a light between two reflection surfaces is integer multiple of wavelength, the total reflection ratio would be very close to 100%, even every reflection surface only presents small reflection ratio. That is so-called Bragg condition. It only satisfy particular wavelength, for other wavelengths they would mutually cancel due to out-of-phase. All of this result in high transmission ratio/high reflection ratio conditions.
Conventional fiber grating sensor such as Taiwan patent No. 1346772, it is characterized in that it has a circle elastic thin plate and a fiber set under the circle elastic thin plate to transmit signal. The fiber comprises a graded fiber grating pasted on the surface of the circle elastic thin plate, and the center of the graded fiber grating is aligned at the center portion of the circle elastic thin plate. The fiber grating sensor is configured as a displacement-meter. A pole and a spring are connected to the center of the circle elastic thin plate. The displacement of the pole is proportional to the counteractive force generated by the spring. The relation of the counteractive force and the reflection signal of the graded fiber grating is used to determine the displacement. The main disadvantage is that the isolation area and the forced area are completely isolated to protect the sensor, but the physical quantities applied on the circle elastic thin plate would influence sensitivity of the sensor.
A conventional manufacture method of forming a fiber grating sensor for sensing chemical gas is shown in Taiwan patent No. I309297. It is characterized in that a manufacturing method of forming a fiber grating sensor for sensing chemical gas comprising steps of:                (1) preprocess: by high pressure hydrotreating to make an optical single modulus fiber with better sensitivity;        (2) grating process: writing a fiber grating on the preprocessed optical single modulus by phase mask method;        (3) polishing shell: polishing the shell of fiber until it reaches required diameter; and        (4) plating: plating the polished fiber grating to grow a cover layer outside the polished fiber, after a certain plating period of time, washing out acid liquid on the surface of fiber grating by deionized water, and drying the fiber surface by nitrogen.        
A conventional pressure sensing device is disclosed in Taiwan patent No. I247101. It comprises a fiber Bragg grating with predetermined length according to different requirement and a side-press pressure sensor. The side-press pressure sensor has a hollow cylinder shell, and two sides of the shell are set with at least one opening. Elastic polymer is stuffed inside the opening of the shell. A hard plate is set on polymer end to ensure that a fiber grating is covered by the polymer and one end thereof is coupled to the hard plate and another end thereof extends outward the shell. The pressure sensing device can be applied to detect pressure, water lever or depth underwater.
Inventor of the present invention realized the aforementioned disadvantages and developed the pressure detecting apparatus made by 3D printing technologies being able to be used in dangerous areas.